Method for floating and drying a web

ABSTRACT

A method and apparatus for floating and drying a flexible web having a coated layer thereon, which employs an air-impinging device comprised of a plate having a plurality of slots or small holes therethrough and communicated with a plenum chamber supplied with air from an air source. The dimensions of the slots in the plate are defined according to predetermined values so that the drying effect of the air impinging on the coated web is maximized.

United States Patent 1 Minoda et al.

[ METHOD FOR FLOATING AND DRYING A WEB [75] Inventors: Minoru Minoda; Tetsuo Yoshida;

Hiroshi Chikamasa, all of Minami Ashigara-Machi, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Minami-Ashigara-Shi, Kanagawa,

22 Filed: Dec. 29, 1971 21 Appl. No.: 213,677

[30] Foreign Application Priority Data Dec. 29, l970 Japan 45/121446 I52 U.S. Cl. 34/10, 34/156 511 int. Cl. F26b 3/10 [58 Field of Search 34/156, 10, 160

[56] References Cited UNITED STATES PATENTS Milligan et al 34/160 5] Nov. 13, 1973 v 3,435,539 4/1969 Van Bouwel et al. 34/160 3,672,066 6/l972 Stephansen 34/156 3,525,164 8/1970 Brown... 34/155 Primary Examiner-Carroll B. Dority, Jr. Assistant Examiner-Larry l. Schwartz Attorney-Richard C. Sughrue et al.

[57] ABSTRACT A method and apparatus for floating and drying a flexible web having a coated layer thereon, which employs an air-impinging device comprised of a plate having a plurality of slots or small holes therethrough and communicated with a plenum chamber supplied with air from an air source. The dimensions of the slots in the plate are defined according to predetermined values so that the drying effect of the air impinging on the coated web is maximized.

2 Claims, 3 Drawing Figures 1 METHOD FOR FLOATING AND DRYING A WEB BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for floating and drying a flexible web having a coated layer thereon, and more particularly to a method and apparatus for floating and drying a flexible web such as a film base of baryta paper and the like having an emulsion layer of set colloidal solution, without contacting the surface thereof by maintaining static air between the web and an air supply header.

2. Description of the Prior Art in the process of manufacturing photographic photosensitive material such as photographic film, and particularly in the drying process, the flexible web on which the photographic emulsion is to be coated often becomes subject to various kinds of defects such as surface defects, such as uneveness in drying of the surface of the layer, scratches, abrasions, press marks, creases, and other defects on the surface of the layer and the web, as well as photographic quality defects such as static fog, press fog, friction fog and other defects. These defects are caused by the high web feeding speed presently being used and the recent improvement in the quality of the photographic material being produced. These surface and photographic quality defects are prominent, particularly in the preparation of photographic material of high sensitivity, such as X-ray film.

In order to prevent the above-described defects, a novel method of floating and drying the web has been put into practice recently. in the recently introduced method, the web is floated and dried by impinging air flow, thereby preventing the surface thereof from contacting any part of the drying during the drying process of the manufacture of photographic photosensitive materials.

Various methods have been utilized for practicing the conventional air support type web floating and drying method. The basic technique most common to the conventional floating and drying methods is to support the web by an air flow impinging on the web out of an air supply header, with a static air pressure being maintained between the air supply header and the web. That is, the air pressure between the air supply header and the web is balanced with the weight of the web having the coated layer thereon. The drying of the layer coated on the web is carried out by the air impinging from the air supply header for supporting the web or by another air stream impinging on the web out of another air supply header.

The air impinging device is generally composed of a flat or cylindrical or curved plate having a series of slots or small holes for blowing air therethrough. In the case of the slots, the slots are arranged so that the longitudinal direction thereof is at right angles to the web feeding direction. In the case of the small holes, the holes are arranged uniformly over the entire plate surface so that a uniform air impingement is provided on the surface of the web. Although the force for supporting the web is dependent on the ratio of the slots or holes, that is, the total impinging area, to the entire area of the plate, and the larger the ratio, the stronger the support force and the faster the drying effect, the efficiency of the drying with respect to the amount of air used therefor is greatly reduced as the ratio increases, due to the mutual interference between the air jets. Accordingly,

the optimum ratio of the total impinging area to the total area of the plate is from 0.8 percent to 5 percent, particularly, from 1 percent to 3 percent.

The slots type air impingement method used in conventional nozzle-jet drying processes has been advantageous in that the web is uniformly dried. On the other hand, it has been difficult to provide a stable air float with good air impinging efficiency by the slots due to the fact that the ratio of the area of the slots to the entire area of the plate is less than 3 percent, according to the above method.

The multi-hole-type air impingement method is a method particularly suitable for providing a uniform drying air stream to the layer coated on the web. This method is advantageous in the case where the web is fed by an ordinary roller support. However, when the multi-hole-type air impingement method is applied to the air support type web feeding and drying system, uneveness in the drying effect appears on the coating surface of the web, which results in uneven fog on the photographic film and a reduction of drying efficiency. This reduction in drying efficiency is caused mainly by the interference between the individual air jets for maintaining static air pressure beneath the web. This reduction in drying effect will be described hereinbelow.

When the static air pressure is maintained at a value not less than 5 mm H O, the central portion of the web is supported by the air pressure of not less'than 5 mm H O. In order to maintain this pressure between the web and the air supply header, the air impinging flow at the edge portions of the web is influenced by the lateral air flow coming fromthe central portion of the web resulting frqm the air impinging flow at the central portion of the web. Thus, the air impinging flow is mutually interrupted and drying unevenness is caused on the coated surface of the web. The air impingement is thus disturbed and the drying efficiency is reduced.

ing to the conventional methaasm effectively support and dry the web at the same time. This difficulty increases as the width of the web increases and the speed of feeding of the web increases accompanied by an increase in the speed of air impingement. Therefore, this difficulty has been a great hindrance to the improvement of the drying process in speed and efficiency, and accordingly, to the improvement of the productivity of high quality photographic material. On the other hand, the improvement of the drying process in speed and efficiency has been greatly desired in order to improve the productivity of photographic film of high quality.

SUMMARY OF THE INVENTION holes are provided in a web supply header plate through which air is impinged.

In accordance with the present invention, the dimension of the oblong holes is particularly defined so that the drying effect is maximized.

Other objects, features and advantages of the present invention will be made more apparent from the following detailed description of the preferred embodiments thereof taken in conjunction with the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view of the web floating and drying section of a first embodiment of the air support type web floating and drying apparatus embodying the method of the present invention;

FIG. 2 is a plan view of the section shown in FIG. 1; and

FIG. 3 is an enlarged plan view showing a portion of the arrangement of the air impinging holes provided in the air impinging plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, there is provided an air floating type web feeding and drying method and apparatus which maintains a static air pressure of notless than mm H O between the web and the air supply header impinging plate, and feeds the web without contacting the surface thereof by the static air pressure maintained therebeneath. The surface of the web is dried by the use of the air, wherein said air impinging plate is provided with a number of oblong or oval small holes for impinging air therethrough. The ratio of the area of the holes in the plate to the entire area of the plate is not more than 5 percent, and the dimensions of the holes are defined in accordance with the following conditions. Note that paragraphs (i) through (vi) define the specific ranges of values for the various dimensions, while paragraph (vii) defines each of the critical dimensions of the embodiment of the present invention:

Dimension or ratio Range Min. Max. (i) a 70 110 (ii) )8 20 +20 (iii) E 3mm 7mm 00% 3 '(v) P/ L5 2.5 (vi) 1 0.7;? 200mm (vii) E is determined so that the impinging holes are uniformly distributed in the sense of area under the conditions set forth above in paragraphs (i) to (vi) where a is the angle between the direction of web feed and the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, [-3 is the angle at which the lengthwise direction of the holes is inclined to the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed 3 is the length of the hole, s is the width of the hole, 1 is the distance between the adjacent holes, p is the distance between the adjacent lines of the holes, and E is the length of lateral discrepancy of the holes in the adjacent lines.

Referring now to the drawing, reference numeral 1 indicates a flexible web having a layer 2 coated thereon. The reference letter A indicates the direction of feed of the web 1, the numeral 3 indicates an air supply plenum chamber for impinging air thereout for drying and supporting the web 1, the numeral 4 indicates an air impinging plate defining the air impinging plenum chamber 3 and extending in parallel with the web 1. Air impinging holes 5 are provided in the air impinging plate 4, as seen in FIG. 2, and a duct 6 is connected to an air supply source for supplying air to plenum chamber 3 from a blower (not shown).

In FIG. 3, the air impinging plate 4 is provided with a plurality of elongated air holes 101, 102, 103, 201, 202 corresponding to the holes 5 of FIGS. 1 and 2, and which are lined along substantially straight lines at the angle a to the web feeding direction. An angle a is an angle between the direction of the feed of the web indicated by arrow A and the direction in which the holes 101, 102, are lined. Angle ,6 is an angle at which the lengthwise direction of the holes is inclined relative to the direction in which the holes are lined. The length If is the longitudinal length of the holes and s is the width of the holes. I is the distance between the adjacent holes on one line of holes perpendicular to the direction of feed of the web. The reference character p is the distance between the adjacent lines of the holes. The character e is the length of lateral displacement of the holes corresponding to each other in the adjacent lines of the holes. These reference characters indicating various dimensions of the holes 101, 102, 103 provided in the plate 4 are all clearly shown in and will be understood from FIG. 3.

The air impinging plate 4 is formed as a flat plane and/or a cylindrical plane having its axis parallel to the lateral direction of the web being fed, that is, parallel to the lines of the holes. The shape, size and the arrangement of the air impinging holes provided in the air impinging plane 4 are so determined that the web is stably supported by the air pressure provided through the holes and that the web is uniformly dried by the air flow impinging therethrough. Further, by the arrangement of the holes, the air flow impinging at the edge portions of the web is not greatly disturbed by the lateral air flow coming from the central portion of the web. These complex and rigid requirements for the dimensions, that is, the shape and size and arrangement, of the air impinging holes provided in the plate 4 are all satisfied by the present invention as described hereinbelow and shown in FIG. 3.

The shape of the air impinging holes 5 (101, 102, in FIG. 3) may be oval, oblong or similar shape which has different lengths in two right-angled directions. The size and arrangement of the holes 5 are so determined that the following relationships between the angle a, the angle B, the length 2 and the width 3' may be satisfied:

a between and inclusive [3 between 20 and +20, inclusive E between 3mm and 7mm, inclusive d /s between 3 and 15 The distributive arrangement of the holes 5 is so determined that the following relationship between the distance I, the distance i and the length 3 may be satisfied m between 1.5 and 2.5, inclusive Tbetween 0.7 and 200mm, inclusive Further, the ratio of the area of the holes 5 to the entire area of the plate 4 is not more than 5 percent, and the width is and the ratio of HF are designed to satisfy the following conditions:

5 between 3mm and 7mm, inclusive d /s between 3 and 15, inclusive, as described above.

The length 6 is determined so that the air impinging holes 5 are uniformly distributed with respect to the area thereof over entire surface of the air impinging plate 4 when the area is totaled along the web feeding direction.

The present invention is also applicable to a web feeding and drying system in which the web has wet layers on the both surfaces thereof. In this case, the apparatus in accordance with the present invention is provided on both sides of the surface of the web to blow air onto the opposite surfaces of the web. In this case, it will be readily understood that the air pressure is made lower on the upper side than the lower side so as to maintain the stable feed of the flexible web.

Now the operation of the web floating and drying method in accordance with the present invention will be described in detail.

Referring to FIGS. 1 and 2, a web 1 having a layer 2 coated thereon on the lower surface thereof is supported by the air flow blowing out of the air impinging holes 5 and fed without contact with the plate 4, during which the layer 2 is dried. The air for supporting the web 1 is introduced into the air impinging plenumchamber 3 through an air supplying duct 6 from a blower (not shown), and is then impinged out of the holes 5 toward the coated surface of the web 1 where it flows laterally on the surface of the layer 2 drying the coating. An air pressure required to support the weight of the web 1 and the tension thereof is maintained between the web 1 and the air impinging plate 4. Thus, the web 1 is supported on the air and fed without contact withh the plate 4. The central portion of the layer 2 on the web 1 is dried by the air flow impinged from the holes 5 located at the center of the plate 4 and the air flow flowing laterally from the holes 5 located out of the central portion of the plate 4.

According to the present invention as described above, the air flow blowing out of one hole does not interfere with the air flow blowing out of another hole. Therefore, the efficiency of drying the web is kept high and the air is used efficiently. Further, the distribution of the holes 5 is such that the web may be subject to a uniform air flow, and accordingly, the layer 2 on the web 1 can be dried uniformly and the web can be floated stably. The web 1 is fed stably and quickly, which results in improvement in productivity of the photographic film. The quality of the potographic film is improved in the sense of uniformity in the photographic property, since the surface defects and photographic chemical defects are obviated.

The present invention will now be described with reference to some practical Examples.

EXAMPLE 1.

1n the air support type web floating and drying apparatus having a cylindrically curved air impinging plate as shown in FIGS. 1 and 2 in accordance with the present invention, the dimensions of the holes as shown in FIG. 3 were selected as follows in the range as defined in the present invention:

The ratio of the area of the holes to the area of the entire plate 2.04%

Conditions ii. B 0

iii. E 5mm iv. Fl} =50mm/5mm =10, in range of 3 to 15.

v. ;T fi=100mm/50mm =2.0, in range of 1.5 to 2.5

vi. i=12omm, between 0.7p(70mm) and 200mm vii. e 28 mm The apparatus as described above is referred to as .Type A-l. In another air support type web floating and drying apparatus the dimensions of the holes as shown in FIG. 3 were selected as follows out of the range as defined in the present invention:

The ratio of the area of holes to the area of the entire plate 2.04

' ii. B 0

iii. 5 5mm iv. Z/ s= 5mm/5mm 1.0, below range of 3 to 15.

v. p/ d= 48mm/5mm 9.6, greater than range of 1.5

vi. Tis below the range of 0.7;"; (33.6mm) to 200mm vii. E 5 mm.

The apparatus as described above is referred to here as Type B-l.

Using the above two types of apparatus Type A-1 and Type B-l an air pressure of 18 mm [-1 0 was maintained between the web and the air impinging plates of the apparatus by supplying impingement air out of the plenum chamber in which static pressure of 50 mm H O was maintained. A polvester film base coated a photographic emulsion layer thereon of 1.6 m wide was floated and dried by the air.

The drving of the web by the Type A-l apparatus was much superior to the drying by the type B-l apparatus in uniformity in drying effect. Further the web was fed much more stably by the Type A-l than the Type 13-1, and flattening and slacking'of the web were not present in the Type A-l apparatus.

EXAMPLE 2 In the air support type web floating and drving apparatus having a cylindrically curved air impinging plate as shown in FIGS. 1 and 2, the dimensions of the holes as shown in FIG. 3 where selected as follows in accordance with the present invention.

The ratio of holes to the area of the entire plate Conditions ii. B 15 iii. E 4.5mm

iv. as 30mm/4.5mm

t o l 5. v. /ql= 60mml30mm= 2, within the range of 1.5 to

vi. T= mm, within the range of 0.75 (42mm) to vii. E 25mm--;

This apparatus is referred to here as Type A-2. Another apparatus was prepared which is referred to as Type B-2" in which the dimensions were selected as follows out of the range defined in the present invention:

The ratio of area of holes to the area of the entire plate 2.18%

Conditions ii. B 0

iii. 5mm

iv. Z7= 5mm/5mm 1, below the range of 3 to 15 (circular holes having a diameter of 5mm) v. FIYI= 45mm/5inm 9, above the range of 1.5 to

= 6.6, within the range of 3 vi. 7= 20mm, below the range of 0.7 3 (31.5mm) to (vii) E=5mm Using the above two types of apparatus Type A-2 and Type B-2 an air pressure of 20mm H O was maintained between the web and the air impinging plates of the apparatus by supplying impingement air to the plenum chamber 3 in which a static pressure of 60mm H O was maintained. A polyester film base coated a photographic emulsion layer thereon of 1.6 m wide was floated and dried by the air.

7 The dry ing of theweb by the s sraas SFTyB A i was much superior to the drying by the apparatus of Type 13-2 in uniformity and in drying effect. Further, the web was floated much more stably by the Type A-2 apparatus than by the Type B-2 apparatus and the flattening and slack of the web were not seen in the apparatus of Type A-2.

EXAMPLE 3 In the air support type web floating and drying apparatus having a cylindrically curved air impinging plate as shown in FIG. 3 the dimension of the holes were determined as follows in accordance with the present invention:

The ratio of area of holes to the entire area of the plate 1.76%

Conditions i. a 90 ii. 3

plate 1.75 percent Conditions i. a 90 ii. [3 0 iii. s mm, within the range of 3mm to 7mm iv. HE 5mm/5mm 1, below the range of 3 to 15 v. 5E= 45mm/5mm 9, above the range of 1.5 to

2.5 vi. T= 25mm, below the range of 0.7? (31.5mm) to vii. E 5mm Using the above two types of apparatus Type A-3 and Type B-3, an air pressure of 16mm H O was maintained between the web and the air impinging plates of the apparatus by supplying impingment air out of the plenum chamber 3 in which a static pressure of 60mm H O was maintained. A polyester film base coated a photographic emulsion layer thereon of 1.8 m wide was fed and dried by the air. The drying of the web by the apparatus of Type A-3 was much superior to the drying by the apparatus of Type 8-3 in uniformity and in drying effect. Further, the web was much more stably fed by the apparatus of Type A-3 than the apparatus of Type B-3 and flattening and slack of the web were not present in the Type A-3 apparatus.

What is claimed is:

l. A method of supporting and drying a coated web comprising the steps of:

maintaining a static air pressure of not less than 5mm H O between the web and an air impinging plate having a number of holes therein, the dimensions and positions of the holes being defined by the ..iqllogiaa aqmgns t. V. V

i. a selected between and inclusive ii. B selected between 20 and +20", inclusive iii. s selected between 3mm and 7mm, inclusive iv. the ratio {Tl selected between 3 and 15, inclusive v. the ratio T/Hselected between 1.5 and 2.5, inclusive vi. 7 selected between 0.7 7 and 200mm, inclusive vii. E is determined such that the air impinging holes are uniformly distributed over the area of the plate according to said conditions, where a is the angle between the direction of feed of the web and the direction of the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, B is the angle at which the lengthwise direction of the holes is inclined to the lines connecting the centers of columns of holes in the direction generally transverse to the direction of the web feed, 2 is the length of the holes, 5 is the width of the holes, I is the distance between the adjacent holes, 5 is the distance between the adjacent lines of the holes, and E is the length of the lateral discrepancy of the holes in adjacent lines of holes, and the ratio of the area of the holes to the entire area of the plate is not more than 5 percent;

feeding the web across the air impinging plate with out contacting the surface of the plate by the static air pressure maintained beneath the plate; and drying the coated surface of the web by use of the air impinging on the film from the holes in the plate.

2. An apparatus for floating and drying a flexible web having a coated layer thereon on a film of air comprising in combination:

a plate having a plurality of openings therethrough, said openings being arranged in a predetermined pattern in accordance with the following conditions:

i. a selected between 70 and 110, inclusive ii. 3 selected between 20 and +20, inclusive iii. If selected between 3mm and 7mm, inclusive iv. the ratio a]; selected between 3 and 15, inclusive v. the ratio HZ selected between 1.5 and 2.5, inclusive vi. i selected between 0.717 and 200 mm, inclusive vii. E is determined such that the openings in said l e. a

uniformly distributed on the plate in accordance with said conditions, where a is the angle between the direction of the feed of the web and the direction of the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, B is the angle at which the lengthwise direction of the holes is inclined to the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, I is the length of the holes,

9 10 E is the width of the holes, Tis the distance between the said plenum chamber, and j holes, 5 E distance between h adjacent means for moving said flexible web across said plate, llnes of holes, and e 18 the length of lateral discrepancy whereby the web is Supported by impinging from of the holes in the adjacent lines of holes, and the ratio of the area of the holes to the entire area of the plate 5 is not more than 5 percent,

a plenum chamber communicating with a pneumatic pressure source, said plate forming one surface of said openings in said plate and simultaneously dries the coated layer thereon without allowing the film strip to contact the surface of the plate. 

1. A method of supporting and drying a coated web comprising the steps of: maintaining a static air pressure of not less than 5mm H20 between the web and an air impinging plate having a number of holes therein, the dimensions and positions of the holes being defined by the following conditions: i. Alpha selected between 70* and 110*, inclusive ii. Beta selected between -20* and +20*, inclusive iii. s selected between 3mm and 7mm, inclusive iv. the ratio d/s selected between 3 and 15, inclusive v. the ratio p/d selected between 1.5 and 2.5, inclusive vi. i selected between 0.7p and 200mm, inclusive vii. e is determined such that the air impinging holes are uniformly distributed over the area of the plate according to said conditions, where Alpha is the angle between the direction of feed of the web and the direction of the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, Beta is the angle at which the lengthwise direction of the holes is inclined to the lines connecting the centers of columns of holes in the direction generally transverse to the direction of the web feed, d is the length of the holes, s is the width of the holes, l is the distance between the adjacent holes, p is the distance between the adjacent lines of the holes, and e is the length of the lateral discrepancy of the holes in adjacent lines of holes, and the ratio of the area of the holes to the entire area of the plate is not more than 5 percent; feeding the web across the air impinging plate without contacting the surface of the plate by the static air pressure maintained beneath the plate; and drying the coated surface of the web by use of the air impinging on the film from the holes in the plate.
 2. An apparatus for floating and drying a flexible web having a coated layer thereon on a film of air comprising in combination: a plate having a plurality of openings therethrough, said openings being arranged in a predetermined pattern in accordance with the following conditions: i. Alpha selected between 70* and 110*, inclusive ii. Beta selected between -20* and +20*, inclusive iii. s selected between 3mm and 7mm, inclusive iv. the ratio d/s selected between 3 and 15, inclusive v. the ratio p/d selected between 1.5 and 2.5, inclusive vi. l selected between 0.7p and 200 mm, inclusive vii. e is determined such that the openings in said plate are uniformly distributed on the plate in accordance with said conditions, where Alpha is the angle between the direction of the feed of the web and the direction of the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, Beta is the angle at which the lengthwise direction of the holes is inclined to the lines connecting the centers of columns of holes in the direction generally transverse to the direction of web feed, d is the length of the holes, S is the width of the holes, l is the distance between the adjacent holes, p is the distance between the adjacent lines of holes, and e is the length of lateral discrepancy of the holes in the adjacent lines of holes, and the ratio of the area of the holes to the entire area of the plate is not more than 5 percent, a plenum chamber communicating with a pneumatic pressure source, said plate forming one surface of said plenum chamber, and means for moving said flexible web across said plate, whereby the web is supported by air impinging from said openings in said plate and simultaneously dries the coated layer thereon without allowing the film strip to contact the surface of the plate. 